Background Cognitive development in early childhood is critical for life-long well-being. Existing cognitive development surveillance tools require lengthy parental interviews and observations of children. Developmental Assessment on an E-Platform (DEEP) is a digital tool designed to address this gap by providing a gamified, direct assessment of cognition in young children which can be delivered by front-line providers in community settings.

Methods This longitudinal study recruited children from the SPRING trial in rural Haryana, India. DEEP was administered at 39 (SD 1; N=1359), 60 (SD 5; N=1234) and 95 (SD 4; N=600) months and scores were derived using item response theory. Criterion validity was examined by correlating DEEP-score with age, Bayley’s Scales of Infant Development (BSID-III) cognitive domain score at age 3 and Raven’s Coloured Progressive Matrices (CPM) at age 8; predictive validity was examined by correlating DEEP-scores at preschool-age with academic performance at age 8 and convergent validity through correlations with height-for-age z-scores (HAZ) and early life adversities.

Findings DEEP-score correlated strongly with age (r=0.83, 95% CI 0.82-0.84) and moderately with BSID-III (r=0.50, 0.39-0.60) and CPM (r=0.37; 0.30 – 0.44). DEEP-score at preschool-age predicted academic outcomes at school-age (0.32; 0.25 – 0.41) and correlated positively with HAZ and negatively with early life adversities.

Interpretation DEEP provides a valid, scalable method for cognitive assessment. It’s integration into developmental surveillance programs could aid in monitoring and early detection of cognitive delays, enabling timely interventions.

Funding SPRING, REACH and COINCIDE were funded through Wellcome Trust, Madura Microfinance Ltd and Wellcome Trust/DBT India Alliance respectively.

The authors have declared no competing interest.

The REACH study, through which baseline and follow-up 1 data was collected, was funded by the Corporate Social Responsibility (CSR) initiative of Madura Microfinance Ltd as part of a larger mission of raising capacity in rural India. The COINCIDE study, through which follow-up 2 was done, is funded by a Team Science Grant from DBT/Wellcome Trust India Alliance [IA/TSG/20/1/600023]. The funding agencies had no involvement in the collection, analysis, and interpretation of data, writing of the report and the decision to submit the paper for publication. All authors had full access to the full data in the study and had final responsibility for the decision to submit for publication.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

IRB of Sangath gave ethical approval for this work

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

All data produced in the present study are available upon reasonable request to the authors